Medical device having a tubular portion

ABSTRACT

A medical device having a tabular portion. In the wall of the tabular portion is a row of slots separated by portions of the wall referred to as “ribs”. The device my be folded by forming a longitudinal groove in the tubular portion separating two longitudinal lobes, with a row of alternating ribs and slots located in each lobe. Each rib in one lobe is then inserted into a slot in tie other lobe.

FIELD OF THE INVENTION

This invention relates to medical devices and more specifically to suchdevices having a tubular potion such as a stent or a catheter.

BACKGROUND OF THE INVENTION

Many medical devices that are inserted into the body have a tubularportion. For example, stents are tubular devices that are inserted intobody ducts for preventing narrowing of the duct lumen, for tutoring adilated lumen or for acting as a substrate for tissue growth. As anotherexample, a catheter may have a tubular portion that may serve totransfer a fluid from outside the body to a body cavity, or for drainingfluid from a body cavity.

The tubular portion of a medical device may have a fixed caliber inwhich it is both delivered and deployed. Alternatively, the tubularportion may be brought into an initial small caliber conformation inwhich it is inserted into the body and delivered to the site where it isto be deployed. Deployment of the device involves expanding the tubularportion to a final larger caliber. Thus, a stent may be brought into aninitial small caliber conformation in which it is inserted into the bodyand delivered to the site where it is to be deployed, and then expanded.

Several stents are known in the art that are delivered to the site oftheir deployment in a small caliber conformation and then deployed in alarge caliber conformation. European Patent No. 0382014 discloses astent made of a flat sheet rolled as a scroll. U.S. Pat. No. 5,151,105discloses collapsing the coils of a helical stent. U.S. Pat. No.5,246,445 discloses tightly wrapping the coils of the stent around acatheter. WO 83/000997 discloses making a stent using curved metal wiresinterwoven into a mesh that is brought into a small caliber conformationby stretching the stent longitudinally. These stents are expanded afterdelivery either by inflating a balloon positioned in its lumen or byself expansion in the case of an elastic stent material when aconstraining mechanism is released, or by a change in temperature in thecase of a thermoexpandable stent material. Most stents tend to elongatewhen brought into the smaller caliber state. This limits the extent towhich the caliber may be decreased before the length of the stentbecomes too long and difficult to deliver. Stents that elongate when thecaliber is decreased subsequently shorten when expanded duringdeployment. This shortening makes accurate positioning difficult.

European Patent 0221570 discloses an expandable stent that is athin-walled tube made from a wire mesh. When a balloon is inflated inthe lumen of the stent, a geometrical deformation of the mesh occurs asthe stent expands radially. However, this stent may remain rigid, makingit difficult to negotiate bends or tortuosities during delivery.Furthermore, the geometrical deformation during expansion may causemultiple weakenings in the wall of the stent thus increasing thepossibility of spontaneous breakage.

U.S. Pat. No. 5,037,427 discloses a stent made from a two-way shapememory alloy. This stent has a transition temperature that is below bodytemperature in which it changes its diameter from a narrow diameter to awide diameter. The stent is inserted into the body under a constant flowof cold fluid in order to maintain the stent in the narrow diameterduring delivery. Once in the stent has been positioned in the desiredlocation, the flow of the cold fluid is stopped and the stent thenexpands as it warms up to body temperature. When the stent is to beremoved, a flow of cold fluid is again applied to the stent causing thestent to return to the narrow diameter conformation. The flow of coldfluid is maintained until the stent is removed from the body.

U.S. Pat. No. 6,042,605 discloses a flexible stent that may be foldedlongitudinally in order to bring the stent into a smaller caliber. Thestent may be maintained in the folded, small caliber state by aguidewire that passes through loops formed along both sides of thelongitudinal fold. After positioning in the body, the guidewire isremoved, and the stent assumes its original large caliber conformation.

SUMMARY OF THE INVENTION

The present invention provides a medical device having a tubular portionsuch as a stent or catheter. In accordance with the invention, the wallof the tubular portion contains at least two rows of slots. The slotsmay be transverse, parallel or oblique to the longitudinal axis of thetubular portion. Each pair of adjacent slots in a row is separated by aportion of the wall material referred to as a “rib”.

The tubular portion of the device may be folded into a small caliber,folded configuration by forming one or more longitudinal grooves in thewall of the tubular portion and inserting ribs in one row into slots inanother row. The formation of a groove creates two longitudinal lobes inthe wall of the tubular portion. In one method of folding the tubularportion, the longitudinal groove is formed so that the each lobecontains a row of slots, with a slot in one row being opposite a rib inthe other row. In another method for folding the tubular portion, thelongitudinal groove is formed so that one row of slots overlies anotherrow of slots in the groove with each of one or more ribs in one rowoverlying a slot in the other row. In this case, each of one or moreribs in one or both of the rows is inserted into the juxtaposed slot inthe other row. The tubular portion may then be maintained in the foldedconfiguration by means of a rod extending through a lumen that is commonto the two lobes.

The tubular portion of the device may be formed from a resilientlyflexible material such as latex or silicone rubber. The tubular portionis in an unstrained state when in the unfolded configuration. Thetubular portion may be maintained in the folded configuration byinserting it into a restraining sleeve. After positioning the device inthe body, the restraining sleeve is removed and the tubular portionreverts to its initial unfolded and unconstrained configuration.Alternatively, the tubular portion may be maintained in the foldedconfiguration by inserting a longitudinal rod or wire through ribs thathave been inserted into slots. After deployment, the wire or rod iswithdrawn so as to allow the tubular portion to regain its unfoldedconfiguration. In yet another alternative, the tubular portion may bemaintained in the folded configuration by coating the tubular portionwith a thin solid coating. After deployment, the coating is mechanicallyor chemically degraded so as to allow the tubular portion to regain itsunfolded configuration.

The tubular portion may also be made from a metal or a polymericmaterial that deforms into its plastic zone when folded. The tubularportion is then unfolded by inflating a balloon in the lumen of thetubular portion.

The tubular portion may also be formed from a super-elastic and/or shapememory alloy such as a nickel-titanium alloy or shape memory polymer.The alloy or polymer is trained to pass from the unfolded configurationto the folded configuration when subjected to a first process such as atemperature change, and to pass from the folded configuration to theunfolded configuration when subjected to a second process. The firstprocess may be, for example, a temporary increase in temperature, andthe second process may be a temporary decrease in temperature.

In its first aspect, the invention thus provides a medical device havingat least a tubular portion, the tubular portion containing two or moreslots separated by ribs.

In its second aspect, the invention provides a method for deploying in abody the medical device according to any one of the previous claimscomprising:

-   -   (a) maintaining the device in the folded configuration    -   (b) positioning the device in the body;    -   (c) bringing the tubular portion into the unfolded        configuration.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to understand the invention and to see how it may be carriedout in practice, a preferred embodiment will now be described, by way ofnon-limiting exile only, with reference to the accompanying drawings, inwhich:

FIG. 1 shows a tubular portion of a medical device in accordance withone embodiment of the invention and a method for folding of the tubularportion from an unfolded configuration to a folded configuration;

FIG. 2 shows another method for folding the tubular portion of a medicaldevice of the invention; and

FIG. 3 shows a tubular portion of a medical device in accordance withanother embodiment of the invention and a method for holding it.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a tubular portion generally indicated by 300 of a medicaldevice, that may be, for example, a stent or catheter. The tubularportion 300 is a thin walled tube. The tubular portion 300 is shown inFIG. 1 a in its unfolded configuration in which it is to be deployed inthe body. The tubular portion 300 encloses a lumen 320. In the unfoldedconfiguration shown in FIG. 1 a, the lumen 320 has a circularcross-section. This is by way of example only, and the device of theinvention may have any cross-sectional shape as required in anyparticular application. For example, a prostatic urethral stent maypreferably have a triangular, oval, or hourglass shape. The tubulardevice may have a cross-sectional shape or size that varies along itslength.

The tubular portion 300 has two rows of slots 330. This is by way ofexample only, and the tubular portion may have any number of rows orslots. Two adjacent slots 330 in a row are separated by a portion 338 ofthe tubular portion 300 referred to as a “rib ”. A slot in one row is ina cross-section with a rib in the other row. A slot in one row and a ribin another row that lie in the same cross-section are referred to hereinas being “contiguous” with each other.

FIG. 1 shows several stages in a first process of bringing the tubularportion 300 into a folded configuration In FIG. 1 b the tubular portion300 is flattened, so as to decrease the cross-sectional area of thelumen 320. In FIG. 1 c, a longitudinal groove 240 is introduced in thetubular portion 300. Formation of the groove 240 separates twolongitudinal lobes 350 along the tubular portion 300. The groove islocated between the two rows of slots so that each row of slots 330 islocated in a different lobe 350. In FIG. 1 d, the lobes 350 are broughtnear to each other. The ribs in each row are then inserted intocontiguous slots in the other row. Inserting the slots 330 into the ribs338 may be done in such a way so as to create a lumen 360 common to bothlobes, as shown in FIG. 1 e. Alternatively, a lumen common to both lobesis not formed as shown in FIG. 1 f. The tubular portion may then bemaintained in the folded configuration by means of a rod or wire 420extending through the lumen 360 that is common to the two lobes as shownin FIG. 1 f.

FIG. 2 shows several stages in a second process of bringing the tubularportion 300 into the folded configuration. In FIG. 2 a the tubularportion 300 is flattened, so as to decrease the cross-sectional area ofthe lumen 320. In FIG. 2 b, a longitudinal groove 450 is introduced inthe tubular portion 300. Formation of the groove 450 separates twolongitudinal lobes 455 along the tubular portion 300. In this method offolding, both rows of slots are located in the groove so that the tworows of slots are juxtaposed, with ribs in one row juxtaposed to slotsin the other row. Each of one or more ribs in one of the two rows maythen be inserted into a slot in the other lobe as shown in FIG. 2 c. Alumen 360 is thus formed from the inserted ribs. Alternatively, as shownin FIG. 2 d, ribs in both rows may be inserted into slots in the otherrow to form a lumen 360.

FIG. 3 shows a tubular portion generally indicated by 500 of a medicaldevice, that may be, for example, a stent or catheter in accordance withanother embodiment of the invention. The tubular portion 500 is shown inFIG. 3 a in its unfolded configuration in which it is to be deployed inthe body. The tubular portion 500 encloses a lumen 520. In the unfoldedconfiguration shown in FIG. 3 a, the lumen 520 has a circularcross-section. This is by way of example only, and the device of theinvention may have any cross-sectional shape as required in anyparticular application. For example, a prostatic urethral stent maypreferably have a triangular, oval, or hourglass shape. Tie tubulardevice may have a cross-sectional shape or size that varies along itslength.

The tubular portion 500 has a plurality of ribs, for example, ribs 538a, 538 b and 538 c. The ribs 538 are joined together by bridges, forexample, the bridges 525 a, 525 b and 525 c. The bridges may be of anyshape as required in a particular application. The number of bridgesbetween adjacent ribs may vary, and in the embodiment shown in FIG. 3,alternates between 1 and 2. The ribs 538 are separated by slots, forexample, the slots 530 a, 530 b and 530 c . The number of slots 530between adjacent ribs can also vary, and in the embodiment shown in FIG.3 alternates between 1 and 2. Thus, for example, the ribs 538 a and 538b are joined by two bridges 525 a and 525 b and two slots 530 a and 530b. Ribs 538 b and 538 c are separated by the bridge 525 c and the slot530 c.

FIG. 3 shows several stages in a first process of bringing the tubularportion 500 into a folded configuration. In FIG. 3 b the tubular portion500 is flattened, so as to decrease the cross-sectional area of thelumen 520. In FIG. 3 c, a longitudinal groove 540 is introduced in thetubular portion 500. Formation of the groove 540 separates twolongitudinal lobes 550 along the tubular portion 500. The groove isformed by pushing the row of single bridges (e.g. the row containing thebridges 525 c) through the lumen 520 of the tubular portion 500. FIG. 3d shows the tubular portion in the folded configuration.

During insertion and delivery of the device in the body, the tubularportion is maintained in the folded configuration. When the tubularportion has been positioned in the body where it is to be deployed, itis made to return to the unfolded configuration. In the case of atubular portion formed from an elastic material, the tubular portion maybe maintained in the unfolded configuration by coating the tubularportion with a polymeric coating. For example, a 2:3 solution ofsilicone rubber and a solvent may be applied to the tubular portion 300and allowed to cure. The solution may be applied by any known methodsuch as brushing, dipping or immersion. After positioning in the body,the coating is degraded either mechanically or chemically to allowexpansion of the tubular portion. Alternatively, the tubular portion maybe maintained in the folded configuration by inserting a wire or rod 420into a lumen of the folded tubular portion as shown in FIGS. 1 g, 2 eand 3 d. After the device has been positioned in the body, the wire orrod 420 is withdrawn and the tubular portion returns to its unfoldedshare.

If the tubular portion is made from a material that deforms into itsplastic zone when brought into the folded configuration, the tubularportion can brought back to the unfolded configuration by introducing aballoon into the lumen of the folded configuration, as shown in FIG. 4a, and inflating the balloon, as shown in FIG. 4 b (not shown).

The tubular portion may also be made from a one or two way shape memoryalloy such as Nitinol. The shape memory alloy is processed by methodsknown in the art so that when the shape memory alloy is in itssuperelastic or austenite state, the tubular portion 300 is in theunfolded configuration. The shape memory alloy is further processed sothat when it is in its soft or austenite state, the tubular portion 300is in the folded configuration. The tubular portion is brought into thefolded configuration by causing it to undergo a transition from themartensite state to the austenite state. This may be accomplished, forexample, by temporarily cooling the tubular portion to a temperature atwhich this transition occurs. After positioning in the body, the tubularportion is brought into the unfolded configuration by causing it toundergo a transition from the austenite state to the martensite state.This may be accomplished, for example, by temporarily heating thetubular portion to a temperature at which this transition occurs.

The shape memory alloy preferably has a transition temperature rangefrom the martensite state to the austenite state and a transitiontemperature range from the state that are near body temperature (around37° C.). This allows the shape memory alloy to undergo a transformationfrom one state to the other at temperatures that essentially do not harmthe surrounding body tissues.

1. A medical device having at least a tubular portion, the tubularportion containing two or more slots separated by ribs.
 2. The deviceaccording to claim 1 wherein the slots are arranged in two or more rowswith a slot in one row being contiguous with a rib in another row. 3.The device according to claim 2 wherein the tubular portion has beenbrought from an unfolded configuration into a folded configuration by amethod comprising: (a) forming one or more longitudinal or helicalgrooves in the tubular portion separating two or more longitudinal lobesso that each row of slots is located in a different lobe; and (b)inserting each of one or more ribs in one lobe into a slot in anotherlobe.
 4. The device according to claim 2 wherein the tubular portion hasbeen brought from an unfolded configuration into a folded configurationby a method comprising: (a) juxtaposing the two rows of slots; and (b)inserting one or more ribs in one row into a slot in the other row. 5.The device according claim 1 wherein the tubular portion is formed froman elastic material.
 6. The device according to claim 5 wherein thetubular portion is maintained in the folded configuration by insertingthe tubular portion in the folded configuration into a restrainingsleeve.
 7. The device according to claim 3 wherein the tubular portionis maintained in the folded configuration by applying a polymericcoating to the tubular portion and allowing the coating to cure.
 8. Thedevice according to claim 7 wherein the coating is mechanically orchemically degradable.
 9. The device according to claim 8 wherein thecoating is applied by spraying, dipping, or brushing.
 10. The deviceaccording to claim 3 wherein the tubular portion deforms into itsplastic zone when brought into the folded configuration.
 11. The deviceaccording to claim 3 wherein the tubular portion is formed from a shapememory material, the tubular portion passing into the foldedconfiguration when the shape memory material undergoes a transition fromthe martensite state to the austenite state.
 12. The device according toclaim 11 wherein the shape memory alloy is a nickel-titanium alloy. 13.The device according to claim 12 wherein the shape memory material is ashape memory polymer.
 14. The device according to claim 1 wherein alumen is formed by the inserted ribs.
 15. The device according to claim14 further comprising a rod inserted into the lumen common so as tomaintain the device in the folded configuration.
 16. The deviceaccording to claim 1 wherein the device is a stent or a catheter. 17.The device according to claim 1 wherein the tubular portion has acircular, triangular or hourglass shape.
 18. The device according toclaim 1 which the tubular portion has a cross-sectional size or shapethat varies along the length of the tubular portion.
 19. A method fordeploying in a body the medical device according to claim 1 comprising:(a) maintaining the device in the folded configuration (b) positioningthe device in the body; (c) bringing the tubular portion into theunfolded configuration.
 20. The method according to claim 19 wherein thetubular portion is formed from an elastic material, and wherein arestraint is applied to the tubular portion in the folded configurationso as to maintain the tubular portion in the folded configuration andwherein bringing the device into the unfolded configuration involvesremoving the restraint.
 21. The method according to claim 20 wherein therestraint is applied by inserting the tubular portion in the foldedconfiguration into a restraining sleeve, and wherein removing therestraining sleeve.
 22. The method according to claim 19 wherein therestraint is applied by applying a polymeric suspension to the tubularportion in the folded configuration and allowing the suspension to cureso as to form a coating to the tubular portion and wherein bringing thetubular portion into the unfolded configuration involves degrading atleast a portion of the coating.
 23. The method according to claim 22wherein the polymeric coating is applied by spraying, dipping orbrushing.
 24. The method according to claim 19 wherein the tubularportion is made from a shape-memory material that has been trained topass from the unfolded configuration to the folded configuration whensubjected to a first process and to pass from the folded configurationto the unfolded configuration when subjected to a second process, andwherein bringing the tubular portion from the unfolded configuration tothe folded configuration involves applying the first process, andwherein bringing the tubular portion from the folded configuration tothe unfolded configuration involves applying the second process.